Plastic bag among garbage found at bottom of the Mariana Trench

Post-consumer plastic has been discovered at the bottom of the Mariana Trench, the deepest point in the ocean.

The Trench, which extends nearly 36,000 feet – or 10 kilometres – down in a remote part of the Pacific Ocean, was the subject of a recent study that revealed that a single-use plastic bag was found at the bottom, making it the deepest known piece of plastic trash.

Scientists found it by looking through the Deep-Sea Debris Database, a collection of photos and videos gathered from 5,010 dives by deep-sea submersibles and remotely operated vehicles over the past 30 years. The images and videos were recently made public by the Japan Agency for Marine-Earth Science and Technology.

Of the classifiable debris logged in the database, plastic was the most prevalent, and plastic bags in particular made up the greatest source of plastic trash. Other debris came from material like rubber, metal, wood, and cloth, and some is yet to be classified.

“We expected it but it’s still surprising that we found these pieces of plastic bag in the Mariana Trench, that is over 10,000 metres deep,” said Sanae Chiba, the study’s lead author. “It’s the deepest part of the ocean where only the highest technology submersible can reach.”

While plastic can enter the ocean directly, such as trash blown from a beach or thrown overboard from ships, a study published in 2017 found that most of it is flowing into the sea from rivers that run through heavily populated regions.